Making formaldehyde from methylene chloride



Patented Aug. 7, 1928.

UNITED STATES PATENT OFFICE.

ERICK KRAUSE AND KOLOMAN ROKA, OF CONSTANCE, GERMANY ASSIGNOBS TO THE FIRIEOF HOLZVERKOHLUNGS-INDUSTRIE AKTIEN-GE SELLSCHAFT, OE CONSTLNOE, BiADENEA, GERMANY, A CORPORATION OF GERMANY.

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No Drawing. Application filed October 23, 19 24. Serial No. 74 5,4923, and in Austria September 17, 1921.

This application is a continuation in part of 'our application 585,802 filed September 1, 1922. in which we have claimed a process for making formaldehyde by reacting meth- 5 ylene chloride in presence of water in a closed vessel at higher temperatures. This reaction may be improved by adding to the reaction mixture substances neutralizing the hydrochloric acid formed during'the reaction but not acting upon the formaldehyde produced.

By experiments we have however found, that for binding the hydrochloric acid pro-- duced during the reaction also such neutralizing substances may be employed, which generally do act upon formaldehyde.

Such substances are for instance strongly alkaline materials such assolutions of alkali-metal hydroxides, ammonia, sodium carbonate and the like. Also lead oxide, which in itself is not strongly alkaline but in reactions of organic chemistry produces the same efiects as strongly alkaline substances is adapted for neutralizing the hydrochloric acid produced when making formaldehyde from methylene chloride. The undesirable action of the acid binding sub stances upon formaldehyde as described above may be avoided according'to our invention, if care is takento maintain the reaction liguid weaklyacid or neutral. This can be e ected if the acid binding substances are. added not allat-one time but gradually in the course of the process. The-working temperature may be varied according to the spe-- eial conditions of the reaction but temperatures between 140 and 170 have been found preferable.

When employing ammonia for the neu-, tralization ofthe hydrochloric acid temperatures below 140 C. for instance temperatures between 120 and 140 C. are suflicient.

Example.

' I To 10 kg. methylene chloridein' an autoclave are gradually added 75 1. of an aqueous solution containing 5% ammonia. reaction mixtureis kept at; temperatures of reaction,

The

about -130 to 150 C. and stirred during the until the methylene chloride has disappeared. The obtained solution is weak- 1y acidic and contains formaldehyde. ammonium chloride and asmall amountof hydrochloric acid. The formaldehyde is separated in the usual way from the solution.

To claim:' a l. A (method for making formaldehyde from methylene chloride which consists 1D heating methylene chloride in the presence of water in a closed vessel to temperatures of about 120 to 170 C. and adding acidbinding materials, which are capable of reacting with formaldehyde, gradually in such quantities, that alkaline reaction of the react-ion mixture is avoided.

- 2. A method for making formaldehyde from methylene chloride which consists in heating methylene chloride in the presence of water in a closed vessel to temperatures of about 120 to 170 C. and adding acidbinding materials, which are capable of reacting with formaldehyde, gradually in such quantities, thatthe reaction mixture is a1 ways maintained weakly acid.

3. A method for making formaldehyde from methylene chloride which consists in heating methylene chloride in the presence of water in a closed vessel to temperatures of about 120 to 170 C. and adding strongly alkaline substances, which are capable of reacting with formaldehyde, gradually in such quantities, that alkaline reaction of the reaction mixture is avoided.

4. A method for "king formaldehyde from methylene chloride which consists in heating methylene chloride in the presence of water in a closed vessel to temperatures of about to C. and adding. ammonia gradually in such quantities, that alka line reaction of .the reaction mixture is avoided. y

In testimony whereof we aflix our signatures.

EBICH E. KOLOMAN B KA. 

